1. Field of the Invention
The present invention relates to telephony systems such as those using Voice over Internet Protocol (VoIP). In particular, the present invention relates to upgrading telephony devices.
2. Description of the Background Art
Large Internet Protocol (“IP”) based telephony systems involve numerous telephony devices connected across a network. As improvements are made, the software operable on the telephony devices needs to be upgraded (i.e., these telephony devices need an “image upgrade”). Upgrading the image of the various telephony devices that comprise the telephony system is difficult for numerous reasons.
First, upgrading the entire system over skinny Wide Area Network (“WAN”) pipes is typically time consuming since the image upgrade typically has a large file size. For example, it can take anywhere between hours to days to fully upgrade a large system due to the file size of the upgrade. Since the upgrade requires a relatively large window of time during which upgrading devices will be nonoperational, the upgrade event needs to be scheduled during business off-hours. However, for systems spanning multiple time zones there is no “off-hours” time window when the telephony devices are not used in which to perform the image upgrade.
Second, extended service outages occur due to the time required to perform the image upgrade. For some customers (e.g., hospitals, utilities, etc.), the phone system is so critical that there is simply no off-hour window that is acceptable. As a result, image upgrades are not feasible and do not occur.
Third, since the upgrade image needs to be transported from its source to the telephony switches using a push or a pull mechanism, upgrading the entire system over a WAN can result in a large volume of network traffic relative to normal network traffic (“network flood”). Network floods can have a snow balling effect causing stability issues that interfere with the update process and the regular operation of the telephone system.
Fourth, power failure during the update process can cause inadvertent partial upgrade of the telephony switches and phones, causing system stability issues.